The ecology of freezing tolerance

  • Spring is a very critical period. Plants on open ground may warm under solar radiation (temperatures above 20 °C are possible anytime). If plants took such daytime warming as the arrival of the growing season and gave up their dormant (hardy) state, the next cold spell would kill them.
  • Therefore such plants control their dormancy by a temperature independent "internal calendar" driven by photoperiod (the relative length of night vs. day). Such plants use "photoperiodism" as a safeguard against becoming active at the wrong time.
  • In contrast, snowbed plants are opportunists, they become active whenever the release from snow and temperatures permit.
1 - Photoperiodism prevents the breaking of plant dormancy at the wrong time.